Chemically Inactive Ionic Polymers

In the first part of this section the elucidation of the mechanism will be presented, while the second part will be devoted to a discussion of the effect of cations on the viscoelastic properties. Both of these topics are grouped together because, as will be shown below, the relaxation mechanism of all the polymers discussed here is perfectly normal, i.e., simple molecular flow, [or the a mechanism according to the nomenclature of Ferry (27, 28, 29) and Hoff 37a), and the materials can thus be called chemically inactive. Finally, the work on viscoelasticity of bulk organic polyelectrol5des will be mentioned. The next section will be devoted to a discussion of the viscoelastic properties of materials in which, in addition to the a mechanism, bond interchange (the x mechanism) is also encoimtered, the chemical (hence x) activity being due to catalysis by transition metal ions. 

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The affinity of the polymer-bound catalyst for water and for organic solvent also depends upon the structure of the polymer backbone. Polystyrene is nonpolar and attracts good organic solvents, but without ionic, polyether, or other polar sites, it is completely inactive for catalysis of nucleophilic reactions. The polar sites are necessary to attract reactive anions. If the polymer is hydrophilic, as a dextran, its surface must be made less polar by functionalization with lipophilic groups to permit catalytic activity for most nucleophilic displacement reactions. The % RS and the chemical nature of the polymer backbone affect the hydrophilic/lipophilic balance. The polymer must be able to attract both the reactive anion and the organic substrate into its matrix to catalyze reactions between the two mutually insoluble species. Most polymer-supported phase transfer catalysts are used under conditions where both intrinsic reactivity and intraparticle diffusion affect the observed rates of reaction. The structural variables in the catalyst which control the hydrophilic/lipophilic balance affect both activity and diffusion, and it is often not possible to distinguish clearly between these rate limiting phenomena by variation of active site structure, polymer backbone structure, or % RS. 

Equilibria between various forms of living centres were treated in Chap. 5, Sect. 8.1. Equilibria of similar character control the arrangement and reactivity of all ionic centres. When polymerization-inactive structures participate in the equilibria, the number of active centres is reduced by the equilibrium amount of inactive forms. This phenomenon is usually not considered as termination the unreactive particles are treated as dormant. In the course of polymerization, however, the physico-chemical parameters of the system change as a function of the monomer-polymer transformation. Changes in permittivity, viscosity and the amount of polymer can cause shifts in ionization and dissociation equilibria. The kinetic manifestations of such changes are identical with the occurrence of termination. 

The number of studies which utilize ionic liquid electrol54e in redox capacitor system is still small, probably due to the difficulty to reproduce the pseudo-capacitive reaction in ionic liquid media. While the principle of pseudo-capacitance of conductive polymer electrodes permits to utilize ionic liquid electrolytes, high viscosity and rather inactive ions of ionic liquid may make their pseudo-capacitive reaction slow. The combination of nanostmctured conductive polymer electrode and ionic liquid electrolyte is expected to be effective [27]. It is far difficult that ionic liquids are utilized in transition metal-based redox capacitors where proton frequently participates in the reaction mechanisms. Some anions such as thiocyanate have been reported to provide pseudo-capacitance of manganese oxide [28]. The pseudo-capacitance of hydrous ruthenium oxide is based on the adsorption of proton on the electrode surface and thus requires proton in electrolyte. Therefore ionic liquids having proton have been attempted to be utilized with ruthenium oxide electrode [29]. Recent report that 1,3-substituted imidazolium cations such as EMI promote pseudo-capacitive reaction of mthenium oxide is interesting on the viewpoint of the establishment of the pseudo-capacitive system based on chemical nature of ionic liquids [30]. 

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